In rotary sprinklers there is provided an irrigator head/distribution rotor which is rotatable in order to cover a desired land pattern. Rotary motion is imparted by the force of the irrigated media (typically water) acting in conjunction with a rotary mechanism converting some of the stream energy into rotary motion. Such a rotary mechanism could be a water gear, a ball motor, etc.
However, at times it is desired to slow the rotary motion so as to generate a slow and smooth rotary motion, resulting in a uniform precipitation of the irrigated media. Different mechanisms are known in the art for that purpose. For example there are known mechanisms where counter arrangements are provided for generating a reaction force opposite to the desired rotary force. Other arrangements are known for dampening the rotary motion of the irrigation head by utilizing the shear effect of a viscous material. Slowing rotation speed of the sprinkler results in increased irrigation range and homogeneous water precipitation, as well as reducing wear of moving parts.
Yet another arrangement is disclosed in U.S. Pat. No. 7,111,796 to Olson, directed to a sprinkler, comprising: a nozzle having a fluid path formed between an inlet and an outlet, the nozzle rotatably driven by a pressurized flow of fluid along the fluid path; and a housing separating a magnetic drag coupling assembly from the fluid path, the magnetic drag coupling assembly configured to exert a drag force in opposition to the fluid flow force rotating the nozzle; further including a pressure balancing mechanism within the nozzle assembly to generally neutralize any axial force that might otherwise be imparted to the nozzle by the fluid flow wherein the coupling assembly includes a drive magnet and a reactionary magnet positioned that exert an attractive force upon each other, a drag source acting on said reactionary magnet to provide a resistive force to oppose rotation of the nozzle.
U.S. Pat. No. 7,287,710 discloses a nutating-type sprinkler including a sprinkler head incorporating a nozzle; a spool fixed to the sprinkler head in proximity to the nozzle; a cage assembly loosely mounted on the spool, the assembly including a distribution plate at a first end of the assembly downstream of the nozzle and a first magnet at a second opposite end of the assembly upstream of the spool; a mounting element fixed to the assembly between the first and second ends, an inner edge of the mounting element loosely confined between upper and lower flanges of the spool; and a second magnet fixed to the sprinkler head, axially between the spool and the first magnet.